developed HFO 1234yf which is sold under the brand names OpteonTM yf and Soltice® yf. This low GWP fluorocarbon is also a replacement for R134a for use in mobile air conditioning (MAC) systems in the automotive sector.
References
1. Tavener, S.J. and Clark, J.H., Chapter 5: Fluorine: Friend or Foe? A Green Chemist’s Perspective, in Fluorine and The Environment, Vol. 2, A. Tressaud (ed.), Elsevier, 2006.
2. Sato, K., Naturally Occurring Organic Fluorine Compounds, Tokyo Chemical Industry, April 2016, www.tcichemicals.com.
3. US Patent 1,978,840, A. L. Henne, assigned to General Motors Corp, Oct. 30, 1934.
4. US Patent 2,192,143, T. Midgley, Jr., A. L. Henne, assigned to Kinetic Chemicals Co., Feb. 27, 1940.
5. US Patent 2,062,743, H. W. Daudt, M. A. Youker, assigned to Kinetic Chemicals Co., Dec. 1, 1936.
6. Blasing, T.J. and Jones, S., Environmental Sciences Division, Oak Ridge National Laboratory, doi: 10.3334/CDIAC/atg.033, February 2012.
7. Daikin Industries, Fluorocarbon, www.daikin.com/chm/products/fluorocarbon, May 2016.
8. Refrigerants Environmental Data, The Linde Group, www.linde-gas.com, April 2020.
9. Ashford, P. et al., Chapter 7, Emissions of Fluorinated Substitutes for Ozone Depleting Substance, in: Processes and Product Use, vol. 3, IPCC Guidelines for National Greenhouse Gas Inventories, www.ipcc-nggip.iges.or.jp, 2006.
10. ASHRAE Standard, ANSI/ASHRAE Addenda z, ah, ai, and aj to ANSI/ASHRAE Standard 34-2007, www.ashrae.org, Jan 27, 2010.
11. Smith, M.B. and March, J., March’s Advanced Organic Chemistry - reactions, mechanism and Structure, John Wiley & Sons, 2007.
12. Ebnesajjad, S., Introduction to fluoropolymers: materials, technology, and applications, 2nd ed, Elsevier, New York, 2020.
13. Ebnesajjad, S., Fluoroplastics Vol 1 – Non-melt Processible Fluoropolymers, 2nd ed, Elsevier, 2015.
14. Ebnesajjad, S., Fluoroplastics Vol 2 – Melt Processible Fluoropolymers, 2nd ed, Elsevier, 2015.
15. Kynar® PVDF Fluoropolymer Family, Arkema High Performance Polymers, http://americas.kynar.com, 2020.
16. U.S. Patent 2,810,702, M.F. Bechteld and M. I. Bro, assigned to Du Pont Co, October 22, 1957.
17. Fluoropolymers Market - Global Industry Trends & Forecasts to 2019 www.marketsandmarkets.com, May 2016.
3
Fluorine Sources and Basic Fluorocarbon Reactions
Fluorine represents the most extreme of all elements [1]. It is the most reactive element known to man. It reacts with glass and nearly everything else. Even noble gases such as xenon, krypton and gold are not safe because every one of them reacts with fluorine. Fluorine is quite unique among all other elements because of its properties. It carries its uniqueness into organic substances when fluorine substitutes hydrogen and other elements in their molecules. The first synthesis of fluorine has been attributed to Moissan who exhibited the reactivity of fluorine [2].
The impact of fluorine on other materials, nicknamed superhalogen, is more severe than that of other halogens including chlorine. This chapter describes fluorine ores and the basic chemistry of reactions to produce organic fluorine compounds. Narrow aspects of fluorine chemistry related to the preparation of commercial fluorinated alkanes are discussed. An overview of the polymerization of fluorinated oleffinic monomers is also reviewed. The readers should consult the books and articles cited in this chapter for a broader understanding of fluorine chemistry.
3.1 Role of Fluorine in Fluorocarbons
Fluorine is the most electronegative of all elements at electronegativity of 4 in Pauling units. Electronegativity of other elements are 3.4 for oxygen, 3.2 for chlorine, 2.6 for carbon and 2.2 for hydrogen (Table 3.1) [3]. Extreme electronegativity of fluorine renders its covalent bonds highly polarized such as in C-F. Consequently, fluorine gas attacks nearly every substance and chemical because of very high reactivity. It even attacks noble gases like xenon producing XeFx. It is easy to fluorinate hydrocarbons by fluorine gas, but the intensity of this reaction is too severe to control and causes broad decomposition.
The shortest bond is formed between C and H (0.11 nm) followed by C-F at 0.14 nm. Van der Waals radius (rw) of fluorine substituent is 0.147 nm, shorter than in any other substituent. Van der Waals radius refers to the radius of an imaginary sphere that an atom occupies. The short bond length and rw prevent the development of steric strain in perfluorinated compounds contributing to high thermal stability [3].
Carbon and fluorine form one of the strongest covalent bonds with an average bond energy around 480 kJ/mol. It exceeds the strength of carbon bond with other halogens (Table 3.2). C-F strength is one of the important reasons for high thermal and chemical stability of organic fluorochemicals. The F atoms have just the right size to create a protective shield (or sheath) over the carbon backbone when it is attached directly to the chain like in polytetrafluoroethylene (PTFE). If the F atoms were any smaller or larger than they are, the sheath would not form a regular uniform cove. This F shield protects the carbon chain from attack and confers chemical inertness and stability to PTFE. Fluorinated chemical groups play a similar role in hydrocarbons [5].
Table 3.1 Atomic properties of fluorine and other elements [4].
| Element | Van der Waals, radii, nm | Electronegativity, Pauling |
| F | 0.147 | 3.98 |
| O | 0.152 | 3.44 |
| N | 0.155 | 3.04 |
| C | 0.170 | 2.55 |
| H | 0.120 | 2.20 |
Table 3.2 Atomic properties of fluorine and other elements [4].
| Element | Average bond strength, kJ/mol |
|
